Light-emitting structure

ABSTRACT

A light-emitting structure, comprising a substrate; a first unit and a second unit, separately formed on the substrate; a trench between the first unit and the second unit, comprising a bottom portion exposing the substrate; an insulating layer arranged on the trench, conformably covering the bottom portion and sidewalls of the first unit and the second unit; and an electrical connection, conformably covering the insulating layer, electrically connecting the first unit and the second unit and comprising a bridging portion and a joining portion extending from the bridging portion, wherein the bridging portion is wider than the joining portion and the bridging portion covers the trench, and the joining portion covers the first unit and the second unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application a continuation application of U.S. patent application,Ser. No. 13/230,988, entitled “LIGHT EMITTING STRUCTURE”, filed on Sep.13, 2011, which claims the right of priority based on U.S. provisionalapplication Ser. No. 61/382,451, filed on Sep. 13, 2010, and the contentof which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present application relates to a light-emitting structure, and moreparticularly to a light-emitting structure having at least twolight-emitting units and an electrical connection for connecting thelight-emitting units.

DESCRIPTION OF BACKGROUND ART

A light-emitting diode array is constructed by electrically connectingseveral light-emitting diodes in series or parallel. One diode iselectrically separated from another by a trench or groove. To connectthe separated diodes, metal line(s) or film(s) can be used to span thetrench between the diodes. However, the metal line(s) or film(s) can beeasily damaged during the manufacturing process due to a high aspectratio of the trench.

SUMMARY OF THE DISCLOSURE

An embodiment of the present application discloses a light-emittingstructure, comprising a substrate; a first unit and a second unit,separately formed on the substrate; a trench between the first unit andthe second unit; and an electrical connection, electrically connectingthe first unit and the second unit and comprising a bridging portion anda joining portion extending from the bridging portion, wherein thebridging portion is wider than the joining portion and the bridgingportion is configured to cover the trench, and the joining portion isconfigured to cover first unit and the second unit.

Another embodiment of the present application discloses a light-emittingstructure, comprising a substrate; a first unit and a second unitseparately formed on the substrate, wherein each of the first unit andthe second unit comprises a lower layer composed of a first-typesemiconductor and an upper layer stacked on the lower layer and composedof a second-type semiconductor, the lower layer of the first unitcomprises a first top surface and a first sidewall, the upper layer ofthe second unit comprises a second top surface and the lower layer ofthe second unit comprises a second sidewall; a trench between the firstunit and the second unit, comprising a bottom portion exposing thesubstrate; an isolation layer arranged on the trench, contiguouslycovering the second top surface, the second sidewall and the bottomportion and configured to expose a portion of the first sidewall; and anelectrical connection arranged on and covering the isolation layer,contacting the exposed portion of the first sidewall with the first-typesemiconductor and the second top surface with the second-typesemiconductor to electrically connect the first unit and the second unitin series.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view disclosing a connectionbetween two light-emitting structure units in accordance with anembodiment of the present invention;

FIG. 2 illustrates a top view of light-emitting structure units inaccordance with an embodiment of the present invention;

FIG. 3 illustrates a filling of the trench in accordance with anembodiment of the present invention;

FIG. 4 illustrates a top view of an electrical connection over a trenchin accordance with an embodiment of the present invention;

FIG. 5 illustrates a top view of an electrical connection over a trenchbetween two light-emitting structure units in accordance with anotherembodiment of the present invention;

FIG. 6 illustrates a cross-sectional view of interconnections betweenlight-emitting structure units in accordance with one embodiment of thepresent invention;

FIG. 7 illustrates a cross sectional view of several light-emittingstructure units in accordance with an embodiment of the presentinvention;

FIGS. 8A-8F illustrate steps of forming light-emitting structure unit inaccordance with an embodiment of the present invention; and

FIG. 9 illustrates a cross sectional view of a light-emitting structureunit in accordance with an embodiment of the present invention.

DESCRIPTIONS OF EMBODIMENTS

FIG. 1 illustrates a cross-sectional view disclosing a connectionbetween two light-emitting structure units in accordance with anembodiment of the present invention. Each of the left light-emittingstructure unit 10A and the right light-emitting structure unit 10Bincludes a lower layer (11A, 11B), an upper layer (12A, 12B), alight-emitting junction (13A, 13B) between the lower layer (11A, 11B)and the upper layer (12A, 12B), and a current spreading layer (14A,14B), which are sequentially formed on a substrate (not shown) byepitaxial growth or bonding method such as metal boding, fusion bonding,and glue bonding. The left light-emitting structure unit 10A and theright light-emitting structure unit 10B can be supported by a commonsubstrate or discrete substrates, and electrically separated by a trench15. For example, the light-emitting structure units 10A and 10B can becommonly formed on a single bulk substrate, such as sapphire, GaAs, Si,metal, glass, or PCB; or each light-emitting structure unit is formed onits independent bulk substrate as described aforementioned, while eachindependent bulk substrate can be further integrated together bymechanical gadgets, organic material, metallic material, or anycombination thereof. The trench 15 is formed to reach to, enter in, orpenetrate the substrate or any layer between the units. The trench 15has a cross-sectional profile of at least one rounded edge and/or atleast one chamfered edge. The rounded edge and/or the chamfered edge canbe formed on a single layer or several layers. For example, as shown inthe drawing, the rounded edge and/or the chamfered edge can be formed onthe lower layer 11A and/or the lower layer 11B. However, the roundededge and/or the chamfered edge can be also formed on both of the upperlayer and the lower layer. The rounded edge preferably has a radius Rnot less than 1 μm. The chamfered edge can have two equal or differentbevel lengths (L_(bevel)).

Moreover, a sidewall of the trench is inclined by more than 80 degreeagainst the bottom surface of the lower layer. For example, the angle θbetween the sidewall and the bottom surface of the lower layer, asillustrated in the drawing, is smaller than 80 degree, 70 degree, 60degree, 50 degree, or 40 degree. The angle θ can also fall within aspecific range, such as 80 degree˜70 degree, 70 degree˜60 degree, and 60degree˜40 degree. Besides, the trench may have sidewalls inclined atsimilar or different angles. For example, one sidewall is inclined at anangle of 50 degree˜40 degrees; the other sidewall is inclined at anangle of 60 degree˜50 degree. Provided one or more sidewalls areinclined, the trench can have a trapezoid cross section having a height,a longer side, and a shorter side parallel to the longer side. Theheight is close to the thickness of the lower layer or the totalthickness of the upper layer and the lower layer. For example, theheight is between 1 μm˜10 μm; the longer side has a length of 3 μm˜100μm; the shorter side has a length of 1 μm˜40 μm; the ratio of the longerside to the short side is between 3:1 and 1.5:1. Specifically, theheight is between 4 μm˜9 μm; the length of the longer side is between 5μm˜40 μm; the length of the shorter side is between 2.5 μm˜20 μm.

To build an electrical passage between the units, an electricalconnection 18 bridges the trench 15 and electrically connects any twolayers, which do not belong to the same unit, of the lower layer 11A,lower layer 11B, upper layer 12A, and upper layer 12B. For example, theunits can be coupled together in series connection by bridging the lowerlayer 11A and the upper layer 12B, or the upper layer 12A and the lowerlayer 11B; the units can be coupled in parallel connection by bridgingthe upper layer 12A and upper layer 12B.

To prevent the electrical connection 18 from unintentionally contactingwith other layer, an isolation layer 16 can be also provided on thetrench 15 and some areas near the trench opening, such as thesidewall(s) of the lower layer 11A and/or the lower layer 11B, theedge(s) of the trench 15, the sidewall(s) of the upper layer 12A and/orthe upper layer 12B, the top surface(s) of the upper layer 12A and/orthe upper layer 12B, and/or the bottom surface(s) of the currentspreading layer 14A and/or the current spreading layer 14B. Optionally,an isolation layer 17 can be further provided between the isolationlayer 16 and the electrical connection 18. The isolation layer 17 can beused to fill the empty space between the isolation layer 16 and theelectrical connection 18, to fill voids on the isolation layer 16, tosmooth the outer surface of the isolation layer 16, to fill the trench15, to form a flat plane for laying the electrical connection 18, tocover area(s) not under the shade of the isolation layer 16, to improveESD protection, and/or to support the electrical connection 18.

The isolation layer 16 can have an edge with an acute angle; the layerlaid on the isolation layer 16 therefore can smoothly cover the drop onthe edge of the isolation layer 16. The slope of the edge can releasethe stress concentrated on the layer over the drop. The acute angle canbe less than 90, 80, 70, 60, or 50 degree. Besides the isolation layer16, the isolation layer 17 can also have an edge with an acute angle.

In addition, to protect the electrical connection 18 from oxidation,erosion, and/or damage, a passivation 19 can be formed on the electricalconnection 18. The passivation 19 can cover not only outer surface(s) ofthe electrical connection 18 but also the area beyond the outersurface(s). Specifically, the passivation 19 can be further formed onany surfaces of the isolation layer 17, the current spreading layer 14A,the current spreading layer 14B, the upper layer 12A, the upper layer12B, the lower layer 11A, and/or the lower layer 11B.

FIG. 2 illustrates a top view of light-emitting structure units inaccordance with an embodiment of the present invention. In the drawing,four rectangular light-emitting structure units 1, 2, 3, 4 are deployedin a 2×2 array; however, the shape, the number, and the deployment ofthe light-emitting structure units are only illustrative but not tolimit applications and variations of the present invention.

The light-emitting structure units 1, 2, 3, 4 are laterally separated bytrenches 15. An electrical connection 18 can bridge the trench 15 fromone light-emitting structure unit (for example, unit 3) to anotherlight-emitting structure unit (for example, unit 4) and couple the twounits in series or parallel connection. As shown in cross section AA′,the trench 15 (for example, between units 1 and 4) on which noelectrical connection 18 is formed has steeper sidewalls, therefore,more volume of the light-emitting structure unit resides nearby thetrench 15. In contrast, as shown in cross section BB′, the trench 15(for example, between units 3 and 4) on which the electrical connection18 is formed has less steep sidewalls in comparison with the sidewallsin the cross section AA′. In one embodiment, some of the light-emittingstructure units are removed to form a trench having a ladder-shaped,and/or inclined sidewall. In other words, the trench has areversed-trapezoid or quasi-reversed-trapezoid cross-sectional profile.For example, the method for forming the trench can be selected from wetetching, dry etching, laser machining, diamond scribing, and anycombination thereof. In general, the steeper the sidewall is, theshorter the processing time is taken.

In addition, the less steep sidewall can be formed on either a fulllength trench L_(full) or a partial length trench L_(partial) (asillustrated in FIG. 2). The full length trench L_(full) herein isdefined as a trench having a length similar to the width of thelight-emitting structure unit; the partial length trench L_(partial) isdefined as a trench has a length smaller than the width of thelight-emitting structure unit. For example, L_(partial) is between 10μm˜100 μm; the width of the light-emitting structure unit is between 100μm˜1000 μm; the ratio of L_(partial) to width of the light-emittingstructure unit is between 1:2˜1:10. Moreover, the electrical connection18 can be further connected with a current network 20 through whichcurrent can come from or flow to a position far away from the electricalconnection 18, as shown in FIG. 5.

FIG. 3 illustrates a filling of the trench. In step (1), an isolationlayer 21 and a lower electrical connection 22 a are sequentiallyprovided on a trench 23 which is formed between two light-emittingstructure units 24, 25. The isolation layer 21 can separate the lowerelectrical connection 22 a from contacting with the light-emittingstructure units 24, 25. The lower electrical connection 22 a canelectrically link two light-emitting structure units 24, 25. The lowerelectrical connection 22 a can be formed by deposition and etchingprocesses. Because the trench 23 has a tapered cross section, theinclined portion of the lower electrical connection 22 a thereforeusually is thinner than the flat portions thereof, and can be easilydamaged during following processes. To reinforce the inclined portion ofthe lower electrical connection 22 a, an upper electrical connection 22b is further provided on the lower electrical connection 22 a. The upperelectrical connection 22 b is preferably provided on the top of theinclined portion or within the trench 23, as shown in step (2).

FIG. 4 illustrates a top view of an electrical connection over a trenchbetween two light-emitting structure units in accordance with oneembodiment of the present invention. The electrical connection 250 has abridging portion 250 a over the trench 23 and two joining portions 250b. Each of the two joining portions 250 b is electrically connected toan anode or a cathode on each of the two light-emitting structure units26. The bridging portion 250 a has a BB cross section; the joiningportion 250 b has an AA cross section. The BB cross section has a widthgreater than that of the AA cross section, while the two cross sectionscan have equal or close area for achieving a constant or even electricalcurrent per cross sectional area. For example, the bridging portion 250a has a width of 5 μm˜50 μm; the joining portion 250 b has a width of 3μm˜15 μm while both of them has a thickness close to 8 μm. However, thetwo cross sections can also have different area according to user'srequirements or practical manufacturing processes. The bridging portion250 a can be constructed after the basic electrical connectionmanufacturing process is completed. For example, the electricalconnection 250 over the trench 23 which has inclined sidewalls isfirstly formed by depositing metal on specific areas of the trench 23and the light-emitting structure units 26. But the deposited metal onthe inclined sidewalls of the trench 23 is usually thinner than thedeposited metal on the light-emitting structure unit 26, and thedeposited metal bridging the two light-emitting structure unitstherefore has various cross sectional area. To increase the volume orthe cross sectional area of the metal over the trench 23, anextra-deposition process is further applied on the thinner depositedmetal area to form the bridging portion 250 a as described above.Furthermore, the volume or the cross sectional area of the electricalconnection 250 over the trench 23 can be increased by other methods,such as bonding one or more supplement articles on the thinnerelectrical connection portions, and depositing other material(s). Thesupplement article is such as metal and ceramic. Moreover, the thickerelectrical connection portions can be even thinned down to the levelsimilar to the portions over the trench 23.

FIG. 5 illustrates a top view of an electrical connection 250 over atrench 23 between two light-emitting structure units in accordance withanother embodiment of the present invention. Each of the light-emittingstructure unit 26 includes a lower layer 27 and an upper layer 28 havinga smaller area than that of the lower layer 27. The lower layer 27 has amesa area 29 surrounding the upper layer 28. The light-emittingstructure unit 26 can emit light from a light-emitting layer which ispositioned within the upper layer 28 or between the upper layer 28 andthe lower layer 27. Provided the light-emitting layer is positionedwithin the upper layer 28, the upper layer 28 can include a p-typesemiconductor layer and an n-type semiconductor layer, between which thelight-emitting layer is sandwiched; and the lower layer 27 can include acarrier for supporting the upper layer 28. The upper layer 28 can beepitaxially grown on the lower layer 27, or be integrated with the lowerlayer 27 by glue bonding, metal bonding, fusion bonding, or eutecticbonding. Provided the light-emitting layer is positioned between theupper layer 28 and the lower layer 27, either the upper layer 28 or thelower layer 27 can include a p-type semiconductor layer, and the othercan include an n-type semiconductor layer.

To build a current passage from one light-emitting structure unit toanother, an electrical connection 250 is provided on the twolight-emitting structure units 26. As shown in the drawing, one end ofthe electrical connection 250 is installed on the upper layer 28, andthe other end is installed on the lower layer 27. However, the two endsof the electrical connection 250 can be also installed on two upperlayers 28 or two lower layers 27. The electrical connection 250 can beconstructed by metal, semiconductor, metal oxide, or any combinationthereof. Provided a metal oxide, which has higher transparency than thatof metal, is used to form the electrical connection 250, fewer lightescaping areas are therefore shaded by the electrical connection 250.The metal oxide is such as ITO, IZO, and CTO.

FIG. 6 illustrates a cross-sectional view of interconnections betweenlight-emitting structure units in accordance with one embodiment of thepresent invention. Each light-emitting structure unit 26 includes anupper layer 28 and a lower layer 27 formed on a common substrate 30 byepitaxial growth and/or bonding method. The bonding method includes butnot limited to metal bonding, eutectic bonding, glue bonding, and fusionbonding. A light-emitting zone 31 is sandwiched by the upper layer 28and the lower layer 27. The light-emitting zone 31 can generate lightwhen a bias voltage is imposed on the upper layer 28 and the lower layer27. The light from the light-emitting zone 31 radiates isotropically.Two light-emitting structure units 26 are separated by a trench 23.Provided the two light-emitting structure units 26 are coupled in seriesconnection, an isolation layer 21 is formed on the trench 23 to leavethe electrical connection 250 touching the upper layer 28 of onelight-emitting structure unit 26 and the lower layer 27 of anotherlight-emitting structure unit 26. In this embodiment, the isolationlayer 21 is formed to expose not only the top surface but a portion ofthe sidewall of the lower layer 27. The exposure of the sidewall of thelower layer 27 can increase the contact area between the electricalconnection 250 and the lower layer 27, and accordingly the currentdensity can decrease.

FIG. 7 illustrates a cross sectional view of several light-emittingstructure units in accordance with an embodiment of the presentinvention. The several light-emitting structure units 26 are supportedby a substrate 30. Two neighboring light-emitting structure units 26 areseparated by a trench 23. In the present embodiment, the trench 23 istrapezoid-shaped and has a narrower top opening and a wider bottom. Thelight-emitting structure unit 26 nearby the trench 23 therefore has anundercut sidewall with a degree greater than 90 degree, as shown in thedrawing. In other words, the light-emitting structure unit 26 has areversed trapezoid shape. Provided the light-emitting structure unit 26can emit light from the middle part, the central part, or the upper partof the reversed trapezoid, the light moving backwards can leave the unit26 on the benefit of the undercut sidewalls. The trapezoid-shaped trenchcan be formed by using over etching process.

In accordance with one embodiment of the present invention, thelight-emitting structure unit can include at least a first conductivitylayer (for example, the upper layer), a conversion unit (for example,the light-emitting zone), and a second conductivity layer (for example,the lower layer). Each of the first conductivity layer and the secondconductivity layer has a single layer or a group of multiple layers(“multiple layers” means two or more layers), and the two single layersor the two groups of the multiple layers, which are respectively locatedon the first and the second conductivity layers, have distinctpolarities or distinct dopants. For example, the first conductivitylayer is a p-type semiconductor layer; the second conductivity layer isan n-type semiconductor layer. The conversion unit disposed between thefirst conductivity layer and the second conductivity layer is a regionwhere the light energy and the electrical energy could be transferred orinduced to transfer. The one that the electrical energy can betransferred to the light energy is such as a light-emitting diode, aliquid crystal display, and an organic light-emitting diode. The onethat the light energy can be transferred to the electrical energy issuch as a solar cell, and an optoelectronic diode.

The transferred light emission spectrum of the light-emitting diode canbe controlled by changing the physical or chemical arrangement of onelayer or more layers in the light-emitting diode. The light-emittingdiode can be composed of several materials, such as the series ofaluminum gallium indium phosphide (AlGaInP), the series of aluminumgallium indium nitride (AlGaInN), and/or the series of zinc oxide (ZnO).The conversion unit can be configured to be a single heterostructure(SH), a double heterostructure (DH), a double-side doubleheterostructure (DDH), or a multi-quantum well (MWQ). Besides, thewavelength of the emitting light could be controlled by changing thenumber of the pairs of the quantum well.

The material of the substrate(s) used for growing or supporting thelight-emitting structure unit(s) can include but not limits to germanium(Ge), gallium arsenide (GaAs), indium phosphide (InP), sapphire, siliconcarbide (SiC), silicon (Si), lithium aluminium oxide (LiAlO2), zincoxide (ZnO), gallium nitride (GaN), aluminum nitride (MN), glass,composite, diamond, CVD diamond, diamond-like carbon (DLC) and anycombination thereof.

FIGS. 8A through 8F illustrate a method of forming light-emittingstructure unit(s), or more specific to light emitting diode structures,in accordance with another embodiment of the present invention. Firstly,referring to FIG. 8A, a substrate 41 is provided. The material of thesubstrate 41 can be silicon, silicon carbide, sapphire, arsenide,phosphide, zinc oxide, and magnesium oxide. Then, a 1st semiconductorlayer 42 which is an epitaxy layer of first conductivity, an activelayer 43, and a 2nd semiconductor layer 44 which is an epitaxy layer ofsecond conductivity are formed on the substrate 41. The material of the1st semiconductor layer 42 and the 2nd semiconductor layer 44 includebut not limited to an indium-containing nitride semiconductor, analuminum-containing nitride semiconductor, and a gallium-containingnitride semiconductor. The material of the active layer 43 include butnot limited to indium gallium nitride, indium gallium aluminumphosphide, aluminum gallium nitride, aluminum gallium arsenide, andindium gallium arsenide.

Referring to FIGS. 8B-8D, a multi-step patterning process is performed.Firstly, a first region of the 2nd semiconductor layer 44 is defined sothat the 2nd semiconductor layer 44 has a concave portion 45 therein byphotolithography and etching technology. Then, as shown in FIG. 8C, asecond etching process is performed to etch away partial of the 2ndsemiconductor layer 44 and partial of the active layer 43 until asurface of the 1st semiconductor layer 42 is exposed. Finally, as shownin FIG. 8D, a third pattern process is performed to divide the 1stsemiconductor layer 42 by forming a trench 46 therebetween through thephotolithography and etching technology. After the multi-step patterningprocess, light emitting diode structure are divided with the step-likesidewall profiles as shown in FIG. 8D.

Referring to FIG. 8E, an insulating layer 47 is further formed betweentwo divided light emitting diode structures 40 to cover the step-likesidewalls of the adjacent light emitting diode structures. Wherein, theinsulating layer 47 is made of dielectric material such as siliconnitride, silicon oxide, aluminum oxide, and the combination thereof.Then, as shown in FIG. 8F, a conductive structure 48 is formed on theinsulating layer 47 to electrically connect the 1st semiconductor layer42 of the left light emitting diode structure and the 2nd semiconductorlayer 43 of the right light emitting diode structure in series. Inaddition, a 1st electrode 49 a and a 2nd electrode 49 b can also beformed at the same step or in the different steps while the conductivestructure 48 is formed.

In addition to the patterning process mentioned above, the step-likesidewalls could also be formed by using a gray-tone mask or by ahalf-tone mask. Taking advantage of different opening ratio existing ona single mask, the step-like sidewall profile can be formed through aone-step exposure.

Referring to FIG. 9, through the step-like sidewall structure, light (asindicated by arrows) comes from different angles can be extracted moreeasily because the light can go out to the sidewall of the lightemitting diodes from different angles, and therefore a better lightextraction ability of the light emitting diode structure could beachieved. Besides, because the slope of the step-like sidewalls isgentle, the coverage profile of the insulating layer and the conductivestructure on the light emitting diode can be more uniform.

What is claimed is:
 1. A light-emitting structure, comprising: asubstrate; a first unit and a second unit, separately formed on thesubstrate; a trench between the first unit and the second unit,comprising a bottom portion exposing the substrate an insulating layerarranged on the trench, conformably covering the bottom portion andsidewalls of the first unit and the second unit; and an electricalconnection, conformably covering the insulating layer, electricallyconnecting the first unit and the second unit and comprising a bridgingportion and a joining portion extending from the bridging portion;wherein the bridging portion is wider than the joining portion and thebridging portion covers the trench, and the joining portion covers thefirst unit and the second unit.
 2. The light-emitting structure of claim1, wherein the joining portion has a cross section area equal to orclose to that of the bridging portion.
 3. The light-emitting structureof claim 1, wherein the joining portion and the bridging portion havesimilar thicknesses.
 4. The light-emitting structure of claim 1, whereinthe joining portion is electrically connected to an anode or a cathode.5. The light-emitting structure of claim 1, wherein the bridging portionis thinner than the joining portion.
 6. A light-emitting structure,comprising: a substrate; a first unit and a second unit separatelyformed on the substrate, wherein each of the first unit and the secondunit comprises a lower layer composed of a first-type semiconductor andan upper layer stacked on the lower layer and composed of a second-typesemiconductor, the lower layer of the first unit comprises a first topsurface and a first sidewall, the upper layer of the second unitcomprises a second top surface and the lower layer of the second unitcomprises a second sidewall; a trench between the first unit and thesecond unit, comprising a bottom portion exposing the substrate; anisolation layer arranged on the trench, contiguously covering the secondtop surface, the second sidewall and the bottom portion and exposing aportion of the first sidewall; and an electrical connection arranged onand covering the isolation layer, contacting the exposed portion of thefirst sidewall with the first-type semiconductor and the second topsurface with the second-type semiconductor to electrically connect thefirst unit and the second unit in series.
 7. The light-emittingstructure of claim 6, wherein the isolation layer exposes the first topsurface, the electrical connection contacts the first top surface. 8.The light-emitting structure of claim 6, wherein the electricalconnection has a greater contact area with the first unit than thesecond unit.
 9. The light-emitting structure of claim 6, wherein thefirst unit and the second unit are spatially separated by the trench.10. The light-emitting structure of claim 6, wherein the lower layers ofthe first unit and the second unit are separated from each other. 11.The light-emitting structure of claim 6, further comprising a currentnetwork formed on the second top surface, and the electrical connectioncontacts the current network.
 12. The light-emitting structure of claim1, wherein the sidewalls of the first unit and the second unit areinclines.
 13. The light-emitting structure of claim 1, wherein thejoining portion comprises a first joining portion and a second joiningportion, wherein each of the first unit and the second unit comprises afirst conductivity layer, an active layer, and a second conductivitylayer, the first joining portion connects to the first conductivitylayer of the first unit and the second joining portion connects to thesecond conductivity layer of the second unit.